1. Field of the Invention
The invention relates to a light guide, more particularly to a light guide for use in a keypad.
2. Description of the Related Art
Referring to FIG. 1, R.O.C. Utility Model Publication No. 266654 discloses a light guide 1 for a mobile phone keypad. The light guide 1 is used in combination with a light emitting diode (LED) 19 disposed proximate to a lateral edge of the light guide 1 such that keys (not shown) on a keypad disposed on an upper side of the light guide 1 are illuminated.
Light emitted from the LED 19 is reflected by peripheral walls 111 defining a plurality of holes 11 before it is incident into a hole 12 which is farthest from the LED 19. However, when the light is incident on a spot of the peripheral wall 111, some of the light is reflected thereby while the rest passes therethrough into the hole 11. Therefore, if the light is reflected by the peripheral walls 111 of a greater number of holes 11, the intensity of the light will be weakened, so that the intensity of the light incident into the hole 12 farthest from the LED 19 is weakest. Since the peripheral wall 111 of each hole 11 in the light guide 1 functions to both admit light and reflect light at every spot, and is not provided with any particular proportion of light admission to light reflection, and since there is not any special design with respect to the angle of incident light, light emitted from the LED 19 cannot reach the hole 12 farthest from the LED 19 directly or through a single reflection, thereby resulting in a weaker intensity of the light in the hole 12 farthest from the LED 19, and non-uniform distribution of light among the holes 11, 12. Thus, the brightness of the light illuminating the keys on the keypad is inconsistent.